Lozzo

It keeps the grooves the seals sit in from corroding, normal grease or copper grease will make the seals swell or wash away and also contaminate the brake fluid. Red rubber grease is waterproof, provides corrosion protection for the alloy caliper grooves and won't attack the rubber seals or brake fluid.

Getting the seals into the caliper are a doddle, getting the piston in is easy too, but like everything that moves, it needs lubricaton not only to make it easier to move, but to provide cooling and corrosion protection - that's where the red rubber grease comes in.